While the further adoption of Windows XP Service Pack 2 likely reduced the total number of successful attacks--one study found that online users were better protecting themselves--Internet service providers and consumer-focused groups, such as digital rights advocates and privacy watchdogs, remained wary.

"Although we have made some strides in helping consumers protect themselves, the threats are growing broader and more dangerous, so the risk of failure can be that much more catastrophic," Tatiana Platt, chief trust officer for America Online, said earlier this month regarding the study.

In 2005, the familiar threats of worm epidemics largely subsided. Instead, attacks targeting vulnerabilities in client-side applications--such as Internet browsers and antivirus software--rose to prominence. Data on bot networks revealed that those centrally controlled networks of computers remained a large threat. And, attacks targeting the systems of specific people in government and industry have managed to sneak under the radar of security systems that have been honed to detect mass infections.

Likely the most significant trend in 2005 was the number of data breaches that have resulted in the loss of personal and financial information, attacks only revealed because of the requirements of the State of California's Security Breach Information Act of 2003 (S.B. 1386).

Lax server security has been a key problem for many of the organizations that have lost information. One Web programming error resulted in the University of Southern California exposing approximately 280,000 records containing the personal details of people who applied to the school. Guidance Software revealed earlier this month that information on nearly 4,000 customers had been stolen by attackers that gained access to an improperly configured server.

Consumers' computers became more secure and resilient to worms in 2005, underscoring that the user behind the keyboard remained the weakest link in the chain of security.

Worms and viruses only scored two medium-sized epidemics. The Zotob worm used a flaw in Microsoft Windows' Plug and Play functionality to spread among Windows 2000 PCs in August. Less then two weeks later, law enforcement authorities had arrested two men in Morocco and Turkey in connection with the worm. The latest variant of the Sober virus--which arrives as an attachment to messages claiming to be from the FBI, CIA or German law enforcement--also spread moderately. The message convinced a German computer user to turn himself, and his child pornography collection, into authorities.